This invention relates to non-slip continuously variable torque transmission devices and more particularly to restorably deformable transfer rings which conform to and transfer torque between input and output torque cones or gearsets.
This invention relates to non-slip continuously variable transmissions (CVT""s) of the type illustrated and described in my earlier PCT application which was assigned International Application No. PCT/CA97/00002 and published under International Publication No. WO97/26469. A device of a related type is also disclosed in French patent no. 1,135,629 to N.S.U. Werke Aktiengesellschaft (the xe2x80x9cNSU devicexe2x80x9d).
Unlike earlier CVT""s which were friction devices and could therefore slip, non-slip CVT""s of the type relevant to this invention utilize an input gearset of bevel or conical shape (sometimes referred to as xe2x80x9ctorque conesxe2x80x9d) which transfers torque to a similarly shaped output gearset or to a ring gear through a transfer ring. The transfer ring has many relatively thin laminations about its periphery which are slidably displaceable in a direction generally perpendicular to the transfer ring itself. The laminations are displaced by xe2x80x9cteethxe2x80x9d on the gearsets as they pass between the gearsets to generally conform to the surface shape of the gearsets. In effect therefore the transfer ring is a continually reformable gear, a portion of which gets re-formed as it passes between a gearset.
The transfer ring provides a torque transfer medium having the benefit of a gear type of device in that it transfers torque in a manner similar to the meshing of gears. In other words, torque transfer is substantially mechanical rather than frictional. The transfer ring furthermore will adapt to the pitch anywhere along a gearset by reforming every time it passes through the gearset. The transfer ring can therefore be moved laterally between the input and output gearsets to vary the torque transfer ratio which is a function of the relative diameters of the input and output gearsets at the point of xe2x80x9cmeshingxe2x80x9d with the transfer ring.
In order to be viable, a transfer ring must be robust, simple to manufacture and assemble, capable of being balanced for relatively high speed operation and exhibit a minimum amount of backlash.
The NSU design provides a transfer ring with inner and outer support rings. Generally C shaped laminations are carried between the support rings. The inner support ring has outwardly extending projections straddled by the open end of the C shaped laminations. The outer support ring has inwardly extending projections which are straddled by the open end of the C shaped laminations. The inner and outer rings are not rigidly secured to one another in the NSU design therefore creating severe shortcomings with respect to capability of being balanced for high speed operations and backlash.
My earlier design overcomes some of the inherent shortcomings of the NSU design by rigidly securing inner and outer support rings to one another by radially extending fixed laminations somewhat analogous to spokes on a wheel. One advantage of rigidly securing the inner and outer support rings in that movement therebetween is eliminated thereby reducing backlash. Additionally the inner and outer support rings are maintained in a fixed concentric arrangement making balancing for higher speed operation possible. Furthermore the presence of the fixed laminations reduces the total amount of space available for backlash.
The presence of fixed laminations secured, typically by welding, to the inner and outer support rings does present some problems. Firstly the movable laminations must be in place prior to securing the fixed laminations. The presence of the movable laminations limits access to the fixed laminations for welding. Furthermore the inner and outer support rings must be held concentrical during welding to ensure good fit and balance. Finally the torque transfer capability of the transfer ring is dependent on the strength of the fixed laminations which would suggest the use of relatively thick members however this is contrary to the desirability of thin members to limit gaps between the movable laminations as they pass between the gearsets.
It is an object of the present invention to provide a transfer ring assembly for a non-slip CVT which positively maintains a fixed spatial arrangement between inner and outer rings without requiring fixed laminations to be welded therebetween.
It is a further object of the present invention to provide a member for carrying movable laminations which limits circumferential displacement of the movable laminations and transfers force from the movable laminations simultaneously to the inner and outer rings.
It is a still further object of the present invention to provide a transfer ring assembly which is made up of relatively simple to manufacture components which are easy to assemble without requiring a special fixture to maintain concentricity between inner and outer rings during assembly.
These and other objects and advantages of the present invention will be apparent upon reviewing the detailed description set out below.
A transfer ring for a continuously variable transmission, said transfer ring comprising:
an inner ring;
an outer ring;
a spacer ring;
said inner, outer and spacer rings being substantially coaxial with a transfer ring axis with said spacer ring disposed radially between said inner ring and said outer ring;
said inner and outer rings being secured to said spacer ring to substantially prevent relative movement therebetween;
said spacer ring having a plurality of alternating, non-overlapping, radially inwardly and radially outwardly facing slots extending respectively into inner and outer circumferences thereof; and,
a plurality of laminar segments slidably mounted in each of said radially inwardly and radially outwardly facing slots, said segments being generally radially aligned with and slidable generally parallel to said transfer ring axis and having upper and lower tabs straddling said spacer ring to limit the distance said segments may be slidably displaced.